The present invention relates to an optical pickup device for optically performing recording and/or reproduction of information on various recording media such as CDs (compact disks), DVDs (digital video disks), or MDs (mini disks), and particularly to a device including a high-frequency superposition circuit for performing high-frequency driving of light sources such as laser diodes or the like.
It was conventionally the case with optical pickup devices that when performing recording and reproduction using laser beams obtained by emitting light through semiconductor laser (hereinafter referred to as xe2x80x9claser diodexe2x80x9d), light reflected by optical disks would be returned to the laser diode while such returned light would cause turbulence in modes of the laser diode and lead to generation of noises in signals. For preventing generation of such noise, it is known to employ a high-frequency superposition method for driving the laser diode upon supply of high-frequency current. While devices employing such a method comprise a high-frequency superposition circuit, leakage of oscillating frequency components of the high-frequency superposition circuit to the exterior will result in extraneous emission.
There are known arrangements including measures for preventing such extraneous emission in which the laser diode and the high-frequency superposition circuit are enclosed by a shielding case with a GND (grounding) pattern of this circuit being electrically connected to the shielding case in a direct manner, or in which a line connected to the circuit is drawn out to the exterior from the shielding case, wherein a capacitor is connected to between the line and the GND proximate to a drawing outlet for the line from the shielding case (see, for instance, Japanese Patent Unexamined Publication No. 11-144283 (1999), Japanese Patent Unexamined Publication No. 6-268385 (1994), or Japanese Patent Unexamined Publication No. 9-63088(1997).
However, it is the case with the above-described conventional optical pickup devices employing the high-frequency superposition method that an FPC (flexible printed circuit board), on which a connector for connecting cables for connecting the optical pickup and a control circuit on a set side and a peripheral circuit are provided, is formed as a separated board from a printed board for the high-frequency superposition circuit, and the high-frequency superposition circuit is formed on a small printed circuit. This would lead to increased costs owing to an increase in the number of operating steps and to poor workability of assembly. Moreover, while it is necessary to connect the GND of the high-frequency superposition circuit to a wide and stable GND at a shortest possible wiring distance in order to prevent extraneous emission, the distance was conventionally long and emission was hard to be reduced to a satisfactory level.
The present invention has been made for solving these problems, and it is an object of the present invention to provide an optical pickup device employing a high-frequency superposition method wherein the high-frequency superposition circuit is not provided on a separate printed board other than the FPC that is provided with a connector but is formed on the FPC to thereby decrease the number of operating steps, enable favorable workability of assembly, and thus to achieve decreases in costs. It is another object to provide an optical pickup device with which a GND of the high-frequency superposition circuit can be connected to a wide and stable GND at a short wiring distance to thereby achieve satisfactory effects of preventing extraneous emission.